SHENZHEN, China—There is an unintended consequence of the White House’s trade battle with China: Companies in the Pearl River Delta, the center of China’s manufacturing might, are accelerating toward making higher-quality products to compete against American goods.

In response to tariffs, which make his goods more expensive, Michael Lu of LTS Group plans to trim costs by using more robots at his plants, which make lamps, bulbs and other lighting products sold at American stores. He is also moving low-skilled work elsewhere...